The present invention relates to a head suspension assembly (hereinafter abbreviated as a HSA) and particularly to a HSA mounting a head IC together with a magnetic head, and a magnetic disk apparatus comprising the HSA.
In general, a magnetic disk apparatus comprises a magnetic disk, a spindle motor for supporting, rotating the magnetic disk, a carriage assembly for supporting and driving a magnetic head, a voice coil motor for driving the carriage assembly, and a main flexible printed circuit board (hereinafter called as a main FPC) for electrically connecting the magnetic head to a control section, which are arranged in a case.
The carriage assembly includes a bearing unit attached to the case, and a plurality of HSAs extending from the bearing unit. The magnetic head is mounted on the extended end portion of each HSA. This HSA has an arm made of a thin metal plate spring and having a proximal end portion which is supported on the bearing unit, an elongate suspension extending from the distal end of the arm and supporting the magnetic head on its distal end portion, and an elongate trace adhered on the suspension and arm. The magnetic head is connected to the main FPC through the trace. This trace is constructed by layering a relay flexible printed circuit board on a thin metal lined plate, for example, made of stainless or the like.
The main FPC has a connection end portion fixed on the bearing unit by a screw, and a proximal end portion connected to the control circuit board fixed to the case. Also, the main FPC has a plurality of connection pads provided at the connection end portion, and a plurality of wiring patterns extending from these connection pads to the proximal end portion. Further, the proximal end portion of the trace extending from the magnetic heads is soldered on the connection pads provided at the connection end portion of the main FPC. In this manner, the magnetic heads are electrically connected to the control circuit board and controlled by this control circuit board.
Meanwhile, the head IC (signal processing IC, integrated circuit element) which amplifies a signal read from the magnetic recording medium by the magnetic head is generally equipped on the control circuit board. In contrast, recently, the length of each wiring pattern from the magnetic head to the head IC can be shortened so that the inductances and capacitances of the wiring patterns can be reduced by mounting the head IC on the trace of the HSA near the magnetic head, as shown in Japanese Patent Application KOKAI Publication No. 11-213365, for example. In addition, a proposal has been made for a HSA equipped with a capacitor (capacitor element) for smoothening the power source.
If the head IC is thus equipped on the HSA, total five wiring patterns, i.e., two signal lines, two power lines (Vcc and Vee), and one ground line (GND) are formed on the trace.
Meanwhile, in the main FPC connected with the trace, independent five wiring patterns are provided in correspondence with one trace. Therefore, for example, the main FPC in a magnetic disk apparatus comprising four HSAs has twenty independent wiring patterns and two wiring patterns for VCM, so that the entire width of the main FPC becomes large. Further, this main FPC constructs a movable part which shifts in accordance with rotation of the head actuator. Therefore, if the width is increased, the main FPC undesirably causes a resistance when the head actuator moves.
Also, the FPC forming part of the trace has a structure in which wiring patterns made of copper foil are sandwiched between insulation layers made of polyimide or the like. Further, the wiring patterns of the FPC which is electrically connected with the head IC are covered with insulation layers, a lining plate having a low heat conductivity, and a suspension, so that only poor heat radiation is attained. Therefore, it is difficult to radiate efficiently heat generated from the head IC, and the temperature of the head IC may exceed a guaranteed temperature range. Further, heat from the head IC transfers to the magnetic head so that the characteristics of the magnetic head change, and the lining plate of the trace and the suspension may thermally expand thereby changing the characteristics of the entire HSA.
In addition, if circuits in the head IC that generate heat of high calorie are not provided symmetrically in the right and left sides with respect to the center line of the HSA, thermal expansion is not symmetrical between the left and right sides in the part which supports the magnetic head of the suspension. Consequently, the characteristics of the magnetic head may be deteriorated.
If the head IC and the capacitor are installed on the HSA, the capacitor cannot be thinned more than the head IC because of its structure, and therefore, the capacitor may contact the magnetic disk surface when the magnetic disk apparatus receives an impact or the like and is deformed thereby.